“Let me stress it again. We do not understand why the course of the investigation is mentioned all the time and why it is said that there are some questions for the Russian side to answer. They have presented no questions so far. And Margaret Beckett told me that today. Moreover, when I asked her if I could mention this in public she said yes, that would be fine. So, it is all up to the British investigators. As soon as we receive their questions we'll start answering them,” Mr Lavrov said.

Meanwhile 2 British Airways planes are being checked for radiation levels, as part of the widening probe into Mr Litvinenko's death.

One of the aircraft currently in Moscow has been allowed by the UK authorities to be flown to London.